When a person calls into work sick, is it up to the manager to find someone to work or the employee calling in?

I'd say manager.
But I guess it depends on the kind of work.

It's up to the manager.

Kinda ridiculous to expect the worker to find cover.
I mean if they can't find anyone what's the alternative ?
Show up for work KNOWING you're going to infect everybody else ?

Would you want to work with somebody with a streaming cold or diarrhoea ??

Most times it is the manager, although I feel the person calling in sick should have the responsibility of finding their own replacement

Up to the manager but we know you're just playing hooky

Manager, their job is to manage the work load & employees!

At my work they make it up to us to find coverage

depends on where you work

It depends on where you work...

Yes, or work it themselves.

It the managers responsibility.